[Tinyos-devel] Request for comments: TEP 112

[David Moss]

"For example, the MSP430 defaults to low power mode 3 (LPM3) unless it
detects that Timer A, the USARTs, or the ADC is active, in which case it
uses low power mode 1 (LPM1)."

There's a problem with this wording and implementation. If all timers are
inactive, the MSP430 implementation should default to LPM4. This saves you
~5-10x more energy than LPM3.

Two reasons:  1. TinyOS is a generic operating system that doesn't require
Timers to operate.  2. Wake-on Radio.

Here are a few applications that use LPM4:
 
http://focus.ti.com/lit/an/slla175/slla175.pdf
http://focus.tij.co.jp/jp/lit/an/slaa384/slaa384.pdf
http://www.gaw.ru/pdf/TI/app/msp430/slaa119.pdf

Yes, it takes the microcontroller longer to wake up that crystal in LPM4.
Whether you care or not depends on the end application.  For wake-on radio
type applications, I don't care. For a TV IR remote or interrupt-driven
system, I don't care. I just want the microcontroller in the lowest power
state possible, which is LPM4.  For other applications that need a faster
response time for an external interrupt while no timers are running anywhere
in the application, the McuPowerOverride interface is available and
documented.

-David









-----Original Message-----
From: tinyos-devel-bounces at millennium.berkeley.edu
[mailto:tinyos-devel-bounces at millennium.berkeley.edu] On Behalf Of Prabal
Dutta
Sent: Thursday, June 12, 2008 2:28 PM
To: tinyos-devel at millennium.berkeley.edu
Subject: Re: [Tinyos-devel] Request for comments: TEP 112

Just a reminder that tomorrow is the last day for comments on TEP 112.
 If you have some thoughts but haven't sent them in, please take a few
minutes and send them to me today or tomorrow.  I will consolidate the
feedback and work with the authors.  Thanks again for your
participation in this important process.

- Prabal

On Fri, May 30, 2008 at 11:26 AM, Prabal Dutta <prabal at cs.berkeley.edu>
wrote:
> Dear TinyOS Developers,
>
> I have been asked to shepherd TEP 112 (Microcontroller Power
> Management) through the Community Review process.  This TEP documents
> how TinyOS manages the lower power state of a microcontroller in
> TinyOS 2.x.  Microcontrollers often have several power states, with
> varying power draws, wakeup latencies, and peripheral support. The
> microcontroller should always be in the lowest possible power state
> that can satisfy application requirements.  Determining this state
> accurately requires knowing a great deal about the power state of many
> subsystems and their peripherals.  Additionally, state transitions are
> common.  Every time a microcontroller handles an interrupt, it moves
> from a low power state to an active state, and whenever the TinyOS
> scheduler finds the task queue empty it returns the microcontroller to
> a low power state.  TinyOS 2.x uses three mechanisms to decide what
> low power state it puts a microcontroller into: status and control
> registers, a dirty bit, and a power state override.  TEP 112 documents
> these mechanisms and how they work, as well as the  basics of
> subsystem power management.
>
> Getting feedback from other TinyOS developers is an essential part of
> the TEP process and I am looking for volunteers to read the draft TEP
> and provide feedback to me via e-mail.  I will then synthesize the
> comments and work with the authors to revise the TEP based on your
> feedback.  Getting feedback by June 6th would be ideal.  The hard
> deadline is June 13th.
>
> The current draft of the TEP is linked from the TinyOS homepage:
>
>
http://tinyos.cvs.sourceforge.net/*checkout*/tinyos/tinyos-2.x/doc/html/tep1
12.html
>
> Please contact me by email directly at prabal at cs dot berkeley dot
> edu if you have some feedback.  Thanks for your help!
>
> - Prabal
>
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